EE-IS Seminar

Seminar schedule of the Institute for Silicon Photovoltaics

Seminars take place on Thursdays

at 10:15

in the EE-IS lecture hall: room 227

(Wilhelm-Conrad-Röntgen Campus, 12489 Berlin, Kekuléstr. 5, 1. Floor)

coffee and cookies are available 15 minutes before the seminar.

Please note that are exceptions from this rule, which are highlighted in the seminar plan.


EE-IS seminar announcement

25.04.2019:

Dr. Paul Harten

Status Report Start-up Preparation LPC-Si

 

abstract:

One of the announced goals and key deliverables of the Helmholtz Innovation Lab HySPRINT is the creation of at least one spin-off company during the course of its initial funding period. To this end the HySPRINT team have initiated a start-up preparation project. Within this project we first investigated 44 potential industrial applications of LPC-Si using start-of-the-art innovation management tools. We then identified the most promising industrial implementations of LPC in a short list. With the highest ranking among the shortlisted applications, active matrix flat panel display backplanes turned out to be the most attractive application. We finally applied for federal government funding in order to perform a demonstration in an industrial setting of LPC-Si’s ability to enable better active matrix flat panel display backplanes.


EE-IS seminar announcement

02.05.2019

Nga Phung will speak about

Ionic doping of metal halide perovskite

abstract:

Halide perovskites are extraordinary photovoltaic materials that enabled to prepare solar cells exciding 22% power conversion efficiency. Incorporating small amounts of foreign ions into the mix of precursors used to prepare the perovskite film is a well-known strategy to improve device performance and stability. For example, monovalent cations such as caesium, rubidium and potassium are particularly effective to boost efficiency in state-of-the-art devices. More recently, divalent and trivalent metal cations are attracting growing attention. While this approach of adding foreign ions into the mix of precursors may resemble classical doping of inorganic semiconductors, it seems to have a completely different working mechanism that is peculiar to halide perovskites.

In this work, we explore the ionic doping mechanism of halide. We use advanced characterisation techniques based on synchrotron measurements to understand the impact of foreign ions on the material. Then, we prepare perovskite solar cells to prove the mechanism in state-of-the-art devices. Our devices made from perovskite film prepared from precursor solutions comprising a small amount of strontium and magnesium achieved a step improvement in the open circuit voltage. We were able to demonstrate the positive effect of dopants on the defect chemistry of the material. From this finding, we hope to broaden the understanding of doping in metal halide perovskite in PV application.

 


EE-IS seminar announcement

16.05.2019

Dr. Qin Tan will speak about

Temperature dependent diffusion of residual solvent molecules during CH3NH3PbI3 layer formation and impact on solar cells

Abstract 

Hybrid organic-inorganic metal halide perovskites are usually prepared from solutions. A solution contains precursor salts and solvents such as DMSO and DMF. During the formation of a crystalline perovskite layer, solvent molecules diffuse out. Residual solvent molecules can remain in the crystal lattice and can influence the performance of solar cells. For the analysis of the influence of residual solvent molecules on the performance of solar cells, the amount of residual molecules in perovskite layers shall be measured. In our approach, we focus on the CH3NH3PbI3 system which has the lowest complexity. For formation of the intermediate phase and for defining practically ideal boundary conditions for out-diffusion, a vacuum-assisted treatment was applied. The temperature dependent out-diffusion of DMSO from CH3NH3PbI3 precursor layers was investigated by measuring the S/Pb molar ratio in by high-resolution continuum source absorption spectroscopy (HR-CSAS) and the evolution of the S=O vibrational mode with infrared spectroscopic ellipsometry (IRSE). The diffusion coefficients were extracted by applying a diffusion model in a homogeneous layer. The diffusion coefficient of DMSO in CH3NH3PbI3 amounted to about 10-11 cm²/s at 100°C. The diffusion coefficient was activated by two processes with activation energies of 0.6 and 1.8 eV which can be explained by decomposition of DMSO complexes and by activation of DMSO trapped in the perovskite lattice. The S/Pb molar ratio had, for example, strong influence on the fill factor of solar cells. Furthermore, it seems that some residual DMSO is useful for the preparation of homogeneous CH3NH3PbI3 layers and to passivate defect states in the material. In future, it will be very interesting to apply our approach to complex systems with more cations, different preparation conditions, various layer architectures etc.


EMIL Seminar of the Institute for Nanospectroscopy Summer semester 2017

Location: EE-IS lecture hall (room 227), Kekuléstr. 5, WCRC Berlin-Adlershof,
Time: Monday 14:00